THE MECHANISM OF LIFE 



515 



ovum in the form of a granular mass and there disposes itself in such 

 a manner that it comes into very close contact with the nucleus. 

 But the most interesting fact is that which makes the activity 

 of the nucleus toward the nutrient material apparent, namely, 

 that the former sends pointed, pseudopodium-like processes into 

 the granular mass where the latter touches it, and only in this 

 direction, and thus very greatly 



increases its surface at the A B c 



place of contact with the nu- 

 trient material. If the latter 

 completely surrounds the nu- 

 cleus, the whole surface shows 

 pseudopodium-like processes. 

 Korschelt describes a similar 

 phenomenon, especially as re- 

 gards the nucleus, in a whole 

 series of arthropod and ccelen- 

 terate ova. The interesting 

 behaviour of the nuclei in 

 secreting - cells toward the 

 secreted substances forms a 

 counterpart to these pheno- 

 mena of the ingestion of sub- 

 stance on the part of the 

 nucleus. Here certain relations 

 exist toward the substances 

 produced, which are wholly 

 analogous to those existing in 

 ova toward ingested substances. 

 In the eggs of certain water- 

 bugs, Nepa and Ranatra, there 

 occur peculiar chitinous ap- 

 pendages, the so-called egg- 

 rays, which are formed by cells 

 especially differentiated for this 

 purpose. These cells, of which 

 each two unite into a single 

 cell with two nuclei, termed 

 by Korschelt a douUe cell, 

 assume a considerable size and 

 secrete within their body the 



FIG. 254. A, A row of cells from a root of Pisum 

 sativum. Upon the right side three stages 

 in the formation of a root-hair are shown ; 

 the nucleus lies at the places in question. B, 

 Three cells from the root of Cucurbita pepo. 

 A root-hair is beginning to form upon each 

 cell ; the nucleus lies at the place where the 

 hair projects. C, Root-hair of Cannabii sativa. 

 The nucleus lies at the tip of the hair, where 

 the growth is taking place. (After Haber- 

 landt.) 



mass of chitin. The behaviour 



of the two nuclei in this process is very characteristic (Fig. 

 256, 7). They send out toward the middle, where the secretion is 

 taking place, numerous, frequently branched, pseudopodium-like 

 processes, which increase the nuclear surface upon this side very 

 considerably, while the rest of the surface remains smooth. Such en- 

 largements of the surface of nuclei are wide-spread in the secreting- 



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